﻿<p>The planar surface is an unbounded surface in the direction of <em>x</em> and <em>y</em>. Bounded planar surfaces are defined by using a subtype of <em>IfcBoundedSurface</em> with <em>BasisSurface</em> being a plane.</p>

<blockquote class="extDef">
NOTE&nbsp; Definition according to ISO/CD 10303-42:1992<br>
A plane is an unbounded surface with a constant normal. A plane is defined by a point on the plane and the normal direction to the plane. The data is to be interpreted as follows:
<pre>
   C = Position.Location
   x = Position.P[1]
   y = Position.P[2]
   z = Position.P[3] =&gt; normal to plane
</pre>
and the surface is parameterized as:
<blockquote class="extDef">
<img src="../../../figures/ifcplane-math1.gif.gif" alt="formula" width="141" height="21">
</blockquote>
where the parametric range is -&infin; &lt; <em>u,v</em> &lt;
&infin;. In the above parameterization the length unit for the
unit vectors <b>x</b> and <b>y</b> is derived from the context of
the plane.</blockquote>

<blockquote class="note">NOTE&nbsp; A rectangular bounded planar surface can be defined by an <em>IfcRectangularTrimmedSurface</em> with
<em>BasisSurface</em> being the plane and <em>U1</em> = left bound in <b>x</b>, <em>U2</em> = right bound in <b>x</b>, <em>V</em>1 = lower
bound in <b>y</b>, <em>V2</em> = upper bound in <b>y</b> if viewed into the direction of the negative normal. (assuming the
<em>Usense</em> and <em>Vsense</em> agree to the sense of the basis surface).</blockquote>
<p>The inherited attributes are interpreted as</p>
<ul>
<li><em>SELF\IfcElementarySurface.Position</em> defines the
location and orientation of the planar surface.</li>
<li><em>SELF\IfcElementarySurface.Position.Location</em> defines a
point on the planar surface.</li>
<li><em>SELF\IfcElementarySurface.Position.P[3]</em> defines the
normal of the planar surface.</li>
</ul>

<blockquote class="note">
NOTE&nbsp; Entity adapted from <strong>plane</strong> in ISO 10303-42.
</blockquote>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC1.5
</blockquote>